Modesty and chastity are important virtues for both Muslim men and women, and the Quran instructs both sexes to "cast down their glances and guard their chastity." But with regard to female modesty, the Quran continues, women should "not display their beauty except what is apparent, and they should place their khimaar over their bosoms" [source: BBC].
A khimaar is a veil-like head covering. Many Muslim scholars interpret the command to not display beauty "except what is apparent" as to mean covering only the hair, but not the face and hands [source: BBC]. Women who follow this tradition typically wear variations on the hijab, a scarf-like head covering.
Others interpret the command to place the veil "over their bosoms" to mean that women should cover much more than just the hair. In the time of the Prophet Muhammad, his wives were said to have worn head-to-toe coverings. This is believed to be the origin of the niqab, a full-body covering that reveals only the eyes [source: BBC].
Another Quranic verse commands that people who speak to the prophet's wives must do so behind a screen to ensure "greater purity for your hearts and theirs." Some have interpreted this to mean that even seeing a woman's eyes is an invitation for impure thoughts. That explains the burqa used by some women, which not only covers the entire body but also veils the eyes with a screen. Others point out that if women's faces were meant to be invisible, the Quran would not instruct men to "cast down their glances."
It's important to note that Muslim women are only expected to cover their heads or faces in public but not at home or in the presence of family members, including men [source: BBC].